(1) Field of the Invention
This invention relates to liquid containing bladders that include a plurality of material layers including a liquid impermeable material layer and at least one sealing layer, the sealing layer including a sealing means for sealing punctures that penetrate the sealing layer.
(2) Description of the Art
Containers are routinely used to hold hazardous and non-hazardous liquids such as hydrocarbons (fuels such as gasoline and kerosene, LPG, crude oil, petrochemicals and the like), liquid hazardous wastes, aqueous acidic and caustic materials, industrial feedstocks, foodstuffs such as milk and oils, and a wide variety of additional liquid materials. Such containers often include inert material bladders inside the container to contain the liquid and to prevent the liquid from contacting the container walls which might be liquid permeable or which might react with the liquid held in the container. The liquid bladders also ensure that leaks are prevented in the event the outer container is breached by a perforation, by corrosion or by any other mechanism.
Liquid holding containers that include bladders can be perforated in such a way that both the container and the bladder are perforated in which case the liquid in the bladder is able to leak out of the bladder and the container through the hole or wound. Some containers employ features to minimize liquid leakage in the event a container is damaged. Minimizing liquid leakage can be especially important with fuel holding containers such as fuel tanks where holes or wounds can allow fuel leakage that can swiftly reduce the amount of fuel available to power the vehicle. Such fuel leaks can result in a financial loss of valuable fuel, in environmental contamination, in a risk of fire, or in a total vehicle loss.
Military vehicles (e.g., military aircraft, tanks, trucks and the like) are especially vulnerable to fuel tank damage such as damage during combat as a result of being hit by ballistics, small arms fire, projectile weapons, shrapnel and/or other similar devices. Such damage can include holes, wounds, punctures, tears, piercings, perforations etc. in the vehicle, with those affecting the fuel tank being particularly problematic. Accordingly, many vehicles, military or otherwise, utilize self-sealing fuel tanks to minimize such risks when the fuel tank is perforated. Conventional self-sealing fuel tanks use a thick layer of natural rubber in the center of a bladder wall. When the tank and self-sealing bladder are punctured, fuel from the tank interacts with the natural rubber of the bladder and causes the rubber to swell to an extent that the hole is effectively sealed, thereby preventing further fuel leakage. However, the natural rubber can take a significant amount of time (e.g., 2 minutes or more) to swell sufficiently to seal the puncture. In addition, larger caliber penetrations are not easily sealed by natural rubber sealants. Furthermore, conventional self-sealing fuel tank bladders can be stiff, heavy, and difficult and expensive to install. Therefore, there is need for improved self-sealing liquid bladders.